1. FIELD OF THE INVENTION
This invention relates to improvements in pulse motors, and more particularly in small size pulse motors such as those assembled into electronic watches.
2. DESCRIPTION OF THE PRIOR ART
FIG. 1 shows an example of the prior art pulse motor. In the Figure, R designates a rotor, S.sub.1 and S.sub.2 designate stators, and C designates a drive coil. The rotor R is rotatable about a shaft R.sub.1, and it is diametrically magnetized and has N and S poles formed alternately along its circumference. The stators S.sub.1 and S.sub.2 are U-shaped and disposed to surround the circumference of the rotor R, with their poles P.sub.1 and P.sub.2 facing each other and also their poles P.sub.2 and P.sub.4 facing each other. The drive coil C is would on a bar-like yoke Y facing the poles P.sub.2 and P.sub.4. It is secured at its opposite ends by screws I.sub.1 and I.sub.2 to the stators S.sub.1 and S.sub.2.
With magnetization of the stators S.sub.1 and S.sub.2 to N and S poles alternately in accordance with an alternating pulse signal supplied to the drive coil C, the rotor R is intermittently rotated at a pitch corresponding to its interpole interval due to the attraction and repulsion of its poles.
The prior art pulse motor of the construction of FIG. 1 has a drawback in that the electromagnetic coupling is low, leading to inferior conversion efficiency. In addition, high positional accuracy is required for the individual magnetic poles. Further, since the rotor R is diametrically magnetized, not only the effective magnetization area is small but also there is a restriction that inexpensive rare earth cobalt magnets which are highly anisotropic cannot be used.